Gas turbine engines use igniters with the combustor to induce combustion within the combustion chamber. A diffuser case circumscribes a combustor liner and an igniter access port is provided which can receive an igniter boss that extends between the diffuser case and the combustor liner. The access port is operable to receive an igniter which extends into the combustion chamber.
A traditional igniter boss can be brazed or welded relative to the combustion liner assembly on the outer wall of the liner. This arrangement allows the igniter boss to be rigidly connected to the combustion liner which traditionally has been constructed of metal. The purpose of the igniter boss is to prevent air from going through the combustor inlet hole while still allowing the igniter to move relative to the combustor. The igniter in turn may be bolted to the outer combustor case which in turn may protrude though a sealing igniter ferrule and towards the combustion liner. Such design provides a somewhat sealed arrangement between the igniter and the combustion liner.
The current trend in the aerospace industry is to utilize lighter weight yet stronger strength materials in various componentry of the gas turbine engine. Use of ceramic materials has been but one method to accomplish this goal and such material is being used with increased frequency to replace traditional metal components in the gas turbine engine. However, the introduction of non-metal components, such as those formed of ceramics, creates yet new engineering problems that need to be solved. For example, fusing metal components to other gas turbine engine ceramic components remains an engineering challenge. Such challenges remain elsewhere in commerce and are not limited to the gas turbine engine industry.
Today the use of ceramics as the primary material source for gas turbine engine combustors offers many benefits. However, combustion liner designs where the liner is made of a non-metallic material, such as ceramics, brazing or otherwise fusing a metal igniter boss assembly to the ceramic liner is not possible. The materials are not compatible and they are not fuseable. As such, an alternate attachment scheme is but one engineering challenge that remains to be solved.
It would be helpful to provide an improved ignition system that overcomes the aforementioned problems. It would also be helpful to provide an improved system of mounting an igniter system to an outer combustor case and then seal against a combustor liner using a flexible bellows assembly.
It would further be helpful to provide a flexible bellows igniter seal assembly that improves sealing between a gas turbine engine diffuser case and an outer combustor liner wall that is in turn made of a ceramic matrix composite (CMC).